proposed the world is made up of empty space and tiny particles called atoms
atomic theory of matter
the idea that matter is made up of atoms
made measurements of chemical reactions in sealed containers and observed that the mass of reactants before a reaction was equal to the mass of the products after the reaction
law of conservation of matter
states that when a chemical reaction occurs matter is neither created nor destroyed but only changed
studied compounds and observed that the elements that composed them were always in a certain proportion by mass (the law of definite proportions)
proposed the atomic theory of matter in 1803
systematic approach to answer questions and solve problems
the first step to solving a problem
a testable prediction to explain observation
an explanation based on many observations and supported by the results of many investigations
a fact of nature that is observed so often that it becomes accepted as truth (does not explain why something happens)
discovered that atoms were not tiny solid balls that could not be broken up into parts but are composed of electrically charged particles
atoms of an element that are chemically alike but differ in mass
proposed a model of an atom in which electrons orbited a central, positively charged nucleus
the number of protons in the nucleus of an atom of an element
the sum of the protons and neutrons in the nucleus of an atom
conducted an experiment that showed that the atom is nearly all empty space with a small dense nucleus
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